A forensic pathologist has told a panel that disgraced pathologist Dr Freddy Patel had failed in two main areas during his postmortem examination of Ian Tomlinson, the newspaper vendor who was hit with a baton and pushed to the ground by a police officer during the G20 protests more than three years ago.

Giving evidence to the Medical Practitioners Tribunal Service panel in Manchester – which arranges hearings on behalf of the General Medical Council – Dr William Lawler said the areas of concern involving Patel in the Tomlinson case were "in relation to the heart" and "also his assessment of the degree of coronary artery narrowing".

Lawler said it was not enough to get observations right, there also had to be an interpretation. "You can't get either without the other," he told the panel on Tuesday.

"The object of the exercise, it might sound trite, is to come up with the right answer … [In relation to cause of death] … Therefore, the conclusions drawn have to be correct and they can only be correct if they are based on accurate observation and correct interpretations. Without either of those two possibilities, that conclusion could be proven to be erroneous."

He said pathologists had to be satisfied that observations were correct and "it is clearly relevant in the context of the Tomlinson case".

Lawler added it was not so obvious in previous cases involving Patel. He has previously appeared before GMC fitness-to-practice hearings and was temporarily suspended from the medical register.

A disciplinary panel said on Monday that Patel was dishonest and "liable to bring his profession into disrepute".

In his initial postmortem report, Patel said Tomlinson had died of coronary artery disease. But questions were raised after footage obtained by the Guardian showed Tomlinson being struck with a baton and falling to the ground and a second report was written by the pathologist.

The panel said the cause of death determined by Patel in the case was wrong and it described his conduct as misleading. Findings identified a total of 68 failings in the case by the pathologist.

The panel will determine if Patel's fitness to practise was impaired by reason of misconduct and/or deficient professional performance and will consider whether he should be allowed to continue as a pathologist, be suspended or struck off the medical register.

The panel will review a 10-week suspension of Patel's registration, which was directed in May.

An inquest jury found Tomlinson had been unlawfully killed, and a number of pathologists gave evidence that he died of internal bleeding. None of them agreed with Patel's opinion on the cause of death. The police officer who struck Tomlinson and pushed him to the ground, PC Simon Harwood, was last month cleared of manslaughter following a trial. The officer claimed he had used reasonable force.

Last year, Patel was given a four-month ban for dishonesty and omitting key findings after examining the body of a murder victim who he said had died from natural causes.

On Monday, the panel heard there was a parallel between that case (involving Sally White – the first victim of the "Camden ripper", Anthony Hardy) and Tomlinson's with regard to the examination of injuries and the potential cause of death identified by Patel during autopsies. The panel found in the Tomlinson case that the pathologist had failed to adequately comment on the possible causes of marks of injury, which he had identified, or their possible significance and the possible mode of death.

He also failed to adequately explain that one of the injuries might be the result of a baton strike and therefore it was a possible "significant mark of violence". Patel also failed to explain the contradictory comment "no significant marks of violence" on his report, the panel found.

Patel also failed to adequately describe and explain his report's finding of "three litres of intra-abdominal fluid blood".

Patel has in addition served a three-month suspension for failings in other cases and is no longer on the official register of approved forensic pathologists.

On 6 April 2009, Patel completed a preliminary report into Tomlinson's death. A second report was completed after he received new evidence.

The panel has released its findings on the case, concluding that Patel admitted not including in his first report that he had mentioned to police he had found injuries that could be consistent with a baton strike.

He also did not properly consider or comment on how abdominal bleeding found during the postmortem examination could have led to Tomlinson's collapse and death. Nor did he fully explain how he could have died of a heart attack, or adequately considered any other possible causes of a non-natural death.

The hearing continues in Manchester on Wednesday and is expected to transfer to London on Thursday.